This is a fair point although in my opinion the discussion may go beyond the standard recommendation.
What the OM and SAE standards do not and cannot predict is the environment. All OM can do is give you their best view for normal and heavy duty. Clearly and without much concern, the simple fact that SOA, and all other manufacturers as well, give you a heavy recommended interval tells you that the normal interval is not ideal because their recommended oil will break down or be inappropriate.
This is exactly why OM goes further and says that for your environment you may need to change your viscosity. SOA just makes an educated guess about how and where most people will use the machine, but they also make a guess themselves. Smart by SOA, but it still tells you that even they don’t stay with one viscosity for a certain length of time for all conditions.
An important thing to note is that all SN 5w-30 oils are pretty much the same. Nothing more than variations on a basic standard and for the most part one is as good as the other and therein lies the problem.
Look at any of VOA in BITOG and then UOA for the same oil. They all seem to lose their cSt values but also stay on grade albeit at the low end. Just a fact of life with oil.
If you run for a distance where the oil gets up to temp and stays there then you’re good but for me, I do less than 3 mile one way rides on some days and the oil never gets up to temp aka I’m rich that it is number one reason for thin oil. Dilution dilutes it and lowers the cSt value.
Using, in my case Redline 5w-30, an oil other than garden variety SN oil, I get a much higher cSt so dilution is not as much of a concern. I think the highest cSt oil available at Wally World has a value of 11.1 and many oils are much less. Redline has a value of about 12 and Castrol Euro 0w-30 has a value of about 12.2. These are all within the class for a 30w oil, but at the upper end, while still meeting the class requirements. If M1 or Pennzoil offered a 12cSt with a HTHS of 3+ I’d be tickled to death, but that won’t happen because thin oils help meet CAFE mileage standards.
So thick vs. thin has to do with the analysis and the SOA intimations it has, depending on the use.
